CVE-2026-19484 is a high-severity (CVSS 7.5) CWE-835 vulnerability in @fastify/busboy. A fix is available for @fastify/busboy — see the affected versions and patch details below.
@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-19484.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-19484 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,415 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@fastify/busboynpmDescription
Impact
Versions of @fastify/busboy from 3.1.0 and prior to 3.2.1 are vulnerable to a Denial of Service. The vendored streaming multipart search stores its default skip distance in a Uint8Array(256). A multipart boundary of exactly 252 bytes makes the search needle 256 bytes, and the table entry wraps to zero, so a crafted request keeps the search in a CPU-bound loop and stalls the Node.js event loop. An unauthenticated client can trigger this with a single small request. Applications that use @fastify/busboy to parse multipart/form-data, directly or through @fastify/multipart, are affected.
Patches
Fixed in version 3.2.1.
Workarounds
Validate the multipart boundary before parsing and reject any boundary longer than the RFC 2046 limit of 70 characters (for example at a reverse proxy or in an onRequest hook). Upgrading to 3.2.1 removes the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @fastify/busboy | ≥ 3.1.0&&< 3.2.1 | 3.2.1npm install @fastify/busboy@3.2.1 |
Affected Products
fastify\/busyboyfastifyDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @fastify/busboy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @fastify/busboy to 3.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-19484 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Red Hat products that include @fastify/busboy are not affected by this vulnerability. CVE-2026-19484 is present only in @fastify/busboy versions 3.1.0 through 3.2.0. Analysis of Red Hat product content shows that the supported offerings ship different versions of @fastify/busboy that are outside the affected range.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat OpenShift AI 2.25 | rhoai/odh-dashboard-rhel9:1791853525 | RHSA-2026:87410 |
| Red Hat OpenShift AI 3.4 | rhoai/odh-dashboard-rhel9:1791861020 | RHSA-2026:84734 |
Frequently Asked Questions
Is CVE-2026-19484 in your dependencies?
Find it across npm, including transitive dependencies.